Here is the Original File - University of New Hampshire

Redox Neutral Aminal Formation
Steven Young
Department of Chemistry, University of New Hampshire, Durham, NH
November 5, 2013
Introduction:
Zero valent iron metal, Fe0, can easily be oxidized to Fe2+ by
many substances. In this case, the reduction of onitrobenzaldehyde (2) was investigated by using iron (0) to
reduce its nitro group into its amine. 1
Conclusions:
Scheme II: Reduction of o-aminobenzaldehyde
The Friedlander condensation is a famous and widely used
synthesis in the production of quinolines using oaminobenzaldehydes. n-Butanol as a solvent provides a high yield
and faster reaction rate when reacting pyrrolidine with 2 to
produce 1,2,3,3a,4,9-Hexahydropyrrolo[2,1-b]quinazoline (3). 2
A melting point and 1H NMR was taken of 2 to test for yield and
purity. The 1H NMR spectrum showed resonances for both the
starting material and product. The melting point also showed signs
of impurities due to the melting point being 38.9-39.6°C, whereas
the literature melting point is 32-34°C
Scheme I: Synthesis of Deoxyvasicinone
Aminals such as 3 represent reduced versions of quinazolinone
alkaloids. These are compounds that over recent years, has
attracted attention due to their diverse biological effects. Aminal
3 reacts readily with a strong oxidizing agent like potassium
permanganate to produce deoxyvasicinone (4). 4 is known to
contain antimicrobial, anti-inflammatory and antidepressant
activities in the human body. 3, 4
Results and Discussion:
(2), was produced by reducing o-nitrobenzaldehyde (1), using iron
powder and dilute hydrochloric acid (0.179 M). This method is
known to produce the highest yield of 2 because of the selective
reduction of aryl nitro compounds using iron powder and dilute
acid. 5
The usage of a syringe pump to slowly add o-aminobenzaldehyde
increases the yield. The slow addition of 2 would reduce the
likelihood of the substrate to undergo self-condensation. Originally,
the addition of 2 was supposed to occur over a 24 hour interval, but
due to time restraints to perform the reaction, the addition could
only occur over 80 minutes. This would have lowered the yield of
any 3 formed. 6
In the first step of the reaction, iron (0) acts as the electron donor
whereas HCl acts as the source of H+ ions. The nitro group is
reduced to a nitroso group. The next step includes the reductive
addition of two hydrogen ions to produce the hydroxylamine. In
the last step another reduction occurs, water is eliminated and
the amine is produced. 7
Overall the project contained quite a bit of problems. 2 was
produced in low yield and contained starting material. There were
no signs that 3 was even produced looking at 1H NMR spectra. This
was most likely because 2 was stored for a week at room
temperature, whereas it should have been stored at -20°C. This
mostly likely caused the product to polymerize producing none of
the desired product.
An 1H NMR was also taken of crude 3. Expected resonances were
not observed. 2 is supposed to be stored at -20°C (in dry ice),
because it has a tendency to undergo self condensation at room
temperature. Even at -20°C, 2 will slowly undergo self condensation.
Due to 2 being stored at room temperature for a week, it was highly
likely that most of it polymerized before performing step 2 of the
reaction.
After the first step, 2 was collected in a low yield and contained
impurities. The approximate yield of pure product should have
been approximately 68%. To increase the yield, the reaction could
have been performed at a slower rate.
Scheme III: 1H NMR of o-aminobenzaldehyde
Acknowledgements:
Special thanks to the UNH Chemistry Department for funding the chemicals needed to carry out the project. Thanks to Professor Greenberg with the suggestion on carrying out this project. Also thanks to Deepthi Bhogadhi
and Sarah Joiner for their help providing chemicals and overlooking the project.
References:
1. Agrawal, Abinash, and Paul G. Tratnyek. "Reduction of nitro aromatic compounds by zero-valent iron metal." Environmental Science & Technology 30.1 (1995): 153-160.
2. Hazlet, S. E.; Dornfeld, C. A. The reduction of aromatic nitro compounds with activated iron. J. Am. Chem. Soc. 1944, 66, 1781-1782
3. Chen Zhang, Chandra Kanta De and Daniel Seidel, “o-Aminobenzaldehyde, Redox-Neutral Aminal Formation and Synthesis of Deoxyvasicinone.” Org. Synth. 2012, 89, 274-282
4. Al-Shamma, A.; Drake, S.; Flynn, D. L.; Mitscher, L. A.; Park, Y. H.; Rao, G. S. R.; Simpson, A.; Swayze, J. K.; Veysoglu, T.; Wu, S. T. S. J. Nat. Prod. 1981, 44, 745-747.
5. Marco-Contelles, J.; Pe´rez-Mayoral, E.; Samadi, A.; Carreiras, M. C.; Soriano, E. Chem. Rev. 2009, 109, 2652-2671
6. Hazlet, S. E.; Dornfeld, C. A. The reduction of aromatic nitro compounds with activated iron. J. Am. Chem. Soc. 1944, 66, 1781-1782
7. Becker, H.; Berger, W.; Domschke, G.; Fanghänel, E. (1999): Organikum - Organisch Chemisches Praktikum. Wiley-VCH Verlag GmbH20, ISBN: 3527297197